Radical-functionalized polymer nanofiber composite separator for ultra-stable dendritic-free lithium metal batteries

Abstract

The application of lithium-metal batteries (LMBs) is limited to the high reactivity of lithium with electrolytes and uncontrolled dendritic Li formation. Therefore, to achieve the uniform deposition of Li from metal crystallization nucleation stage is of great significance for the realization of dendritic-free Li anode. Herein, a polymethyl methacrylate (PMMA) precursor grafted with 9-anthracenecarboxylic acid (An) and 4-amino-2,2,6,6-tetramethyl-1-piperidinylox (TEMPO) has been directly electrospun on the surface of the commercial polypropylene (PP) separator to obtain a radical functionalized bilayer porous composite membrane, which is signed as PMMA-An/TEMPO@PP. The radical functional groups of TEMPO can guide the uniform distribution of Li nucleation while the cross-linked An groups can improve the mechanical strength of the composite nanofiber membrane. Furthermore, the three-dimensionally interconnected porous nanofiber network can evenly redistribute the lithium ions when they pass through the composite separator. As a result, at a high current density of 2 mA cm−2, the lithium metal anode achieves a high Coulomb efficiency (97%) for uniform and dendrite-free deposition of lithium, as well as a long-term reversible lithium plating/stripping of 950 h for potential applications in LMBs.